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Re: dinosaur@usc.edu



 If forced (at gunpoint)to come up with a fast
 explanation the sail on Spinosaurus, thermal
 adaptation (heat radiator) would be my first
 hypothesis...sexual/territorial display
 2nd....predator avoidance 3rd. Never would have
 thought of shade, which is why it's fun. 02 iso
 asymmetries?? "limb"? Ya think? Still fun though.
 
--- Renato Santos <dracontes@hotmail.com> wrote:
> 
> > Demetrios Vital wrote:
> > 
> > >How plausible is this behavior considering the
> > environs of
> > >Spinosaurus?  Are there other species of fish
> that
> > congregate in
> > >shade, or other predators that use their shadow
> to
> > hunt?
> > 
> > Well, I'm not all that knowledgeable about the
> > paleoenvironment in that 
> > region of Africa (Baharija Fm.), except that it
> was
> > an estuary. 
> > *Spinosaurus* has as far as we know piscivorous
> > adaptations; I'm just 
> > proposing a modus operandi for the creature's
> > feeding habits based on extant 
> > creatures that approximate its niche (if there are
> > any). In fact, 
> > *Spinosaurus* might as well had brightly colored
> > feet as some herons do to 
> > scare off fish as it waded ;-)
> > Being a big animal and presumably catching big
> fish
> > in murky waters, I think 
> > this way of fishing provided two benefits: fish
> are
> > naturally attracted to 
> > shades as they tend to denote thick vegetation and
> > rocky areas where 
> > land-bound and aerial predators are less likely to
> > attack them (at least 
> > that's what I hear on wildlife shows); the animal
> > could use its shade as a 
> > way to diminish the glare the water's surface
> > produces thus being able to 
> > see the fish more clearly.
> > 
> > >Really interesting speculation.  Is this even
> > remotely provable?
> > 
> > If we had an generous amount of fossil evidence we
> > could look at asymmetries 
> > in oxygen isotope ratios on the ribs or each side
> of
> > the neurapophyses as 
> > these would be exposed to diferent temperatures
> and
> > perhaps even 
> > histological evidence that shows how these
> > temperature differences affected 
> > the bone. But this would only be valid if the
> animal
> > used consistently the 
> > same side of the sail to produce shade. To prove
> > that the animal waded 
> > regularly one could compare the oxygen isotope
> > ratios on the feet and leg to 
> > the ones on for example the pubic bones, with
> > obviously a calibration chart 
> > with results from extant waders, extinct waders
> and
> > non-waders of each type.
> > I am perhaps going out on a limb here but it would
> > be interesting if this 
> > could be done even on an academic standpoint.
> > 
> > Renato Santos
> > 
> >
>
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